云南滇西地区早古生代增生杂岩的厘定及其洋壳俯冲消减作用--基于1∶5万文东幅地质调查的新认识  

Determination and oceanic crust subduction of Early Palaeozoic accretionary complexes in the western Yunnnan Province--New cognition based on the geological survey ofWendong sheet(1∶50000)

作　　者：彭智敏[1] 王保弟[1] 胡金锋 付于真[3] 王国芝[3] 张辑 刘云鹤 张璋[1] 关俊雷[1] 韩文文 PENG Zhimin;WANG Baodi;HU Jinfeng;FU Yuzhen;WANG Guozhi;ZHANG Ji;LIU Yunhe;ZHANG Zhang;GUAN Junlei;HAN Wenwen(Chengdu Institute of Geology&Mineral Resources,China Geological Survey,Chengdu 610081,Sichuan,China;Institute No.280,CNNC,Guanghan 618300,Sichuan,China;Chengdu University of Technology,Chengdu 610059,Sichuan,China)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081 [2]核工业280研究所,四川广汉618300 [3]成都理工大学地球科学学院,四川成都610059

出　　处：《中国地质》2022年第5期1656-1672,共17页Geology in China

基　　金：国家自然科学基金(92055314);中国地质调查局项目(DD20160016,DD20221635)联合资助。

摘　　要：【研究目的】澜沧岩群一直存在较大争议,查明澜沧岩群的物质组成、构造属性、时代及变质变形特征具有重要的意义,为进一步重建特提斯的时空格架提供重要的基础资料。【研究方法】在1∶5万详细野外调查的基础上,系统开展LA-MC-ICP-MS锆石U-Pb年代学等综合研究。【研究结果】查明了澜沧岩群的物质组成及变质变形特征,具有基质+块体的构造混杂岩特征,经历了3期变质变形,整体表现为逆冲推覆-增生造山的构造变形样式。通过碎屑锆石、变酸性岩锆石U-Pb年代学研究,结合已有的研究资料,厘定其形成时代为早古生代。澜沧岩群中高压变质岩的原岩具有岩浆弧、OIB和E-MORB的特征,说明澜沧岩群经历了深俯冲、增生造山作用过程。【结论】结合区域已有的研究资料及本文研究成果,认为澜沧岩群不是基底岩系,而是昌宁—孟连原-古特提斯洋俯冲消减形成的早古生代增生杂岩。This paper is the result of geological survey engineering.[Objection]:The purpose of this study is to reveal the material composition,tectonic nature,age,metamorphism,and deformation of the Lancang Group,which are controversial but of great significance.The results will provide fundamental data for further reconstruction of the spatiotemporal framework of the Tethys.[Methods]Systematically syntheticstudies were performed based on 1:50000 detailed field investigation and Laser Ablash Inductively Coupled Plasma Mass Spectrometer(LA-ICP-MS)U-Pb dating of zircons.[Results]The Lancang Group is characterized by a tectonic mélange with matrix and blocks.It underwent three stages of metamorphism and deformation,overall as athrust nappe accretionary orogen.The formation age of the Lancang group is determined as the Early Paleozoic based on the zircon U-Pb ages from detrital zircons and meta acid rocks and previous research data.The protolith of the high-pressure metamorphic rocks in the Lancang Group has the characteristics of magmatic arc,OIB and E-MORB,indicating that the Lancang Group experienced deep subduction and accretionary orogeny.[Conclusions]Combined with the available research data in this region and the results obtained in this paper,the Lancang Group is not a basement but an Early Paleozoic accretionary complex formed by the subduction of the Changning-Menglian Proto-Paleo-Tethys Ocean.

关 键 词：澜沧岩群 原-古特提斯洋 增生杂岩 早古生代 地质调查工程 滇西 

分 类 号：P534.4[天文地球—古生物学与地层学] P587[天文地球—地质学] P542